/ Dictionary / Index F Frankfurt horizontal: Meaning and Definition of Find definitions for: Frank'furt horizon'tal Pronunciation: [key] the plane established when right and left poria and left orbitale are in the same horizontal plane. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. frankfurter Frankie Related Content Daily Word Quiz: paradox Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language